package LeetCode.题库.中等;

import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;

/**
 * @author 挚爱之夕
 * @version 1.0
 * @implSpec 给你一个由 n 个整数组成的数组nums ，和一个目标值 target 。
 * 请你找出并返回满足下述全部条件且不重复的四元组[nums[a], nums[b], nums[c], nums[d]]
 * （若两个四元组元素一一对应，则认为两个四元组重复）：
 * 0 <= a, b, c, d < n
 * a、b、c 和 d 互不相同
 * nums[a] + nums[b] + nums[c] + nums[d] == target
 * 你可以按 任意顺序 返回答案 。
 * 输入：nums = [1,0,-1,0,-2,2], target = 0
 * 输出：[[-2,-1,1,2],[-2,0,0,2],[-1,0,0,1]]
 * @since 2022 - 10 - 23 - 12:18
 */
public class _18四数之和 {
    public static void main(String[] args) {
        int[] nums = {1, 0, -1, 0, -2, 2};
        int target = 0;
        System.out.println(new Solution18().fourSum(nums, target));
    }
}class Solution18 {
    public List<List<Integer>> fourSum(int[] nums, int target) {
        List<List<Integer>> list = new LinkedList<>();
        if(nums == null || nums.length < 4) return list;
        Arrays.sort(nums);
        int len = nums.length;
        for(int i = 0; i <= len - 4; i++){
            if(i > 0 && nums[i] == nums[i - 1]) continue;
            if((long)nums[i] + nums[i + 1] + nums[i + 2] + nums[i + 3] > target) break;
            if((long)nums[i] + nums[len - 3] + nums[len - 2] + nums[len - 1] < target) continue;
            for(int j = i + 1; j <= len - 3; j++){
                if(j > i + 1 && nums[j] == nums[j - 1]) continue;
                if((long)nums[i] + nums[j] + nums[j + 1] + nums[j + 2] > target) break;
                if((long)nums[i] + nums[j] + nums[len - 2] + nums[len - 1] < target) continue;
                int left = j + 1, right = len - 1;
                while(left < right){
                    long sum = (long)nums[i] + nums[j] + nums[left] + nums[right];
                    if(sum == target){
                        list.add(Arrays.asList(nums[i], nums[j], nums[left], nums[right]));
                        left++;
                        while(left < right && nums[left] == nums[left - 1]) left++;
                        right--;
                        while(left < right && nums[right] == nums[right + 1]) right--;
                    }else if(sum < target){
                        left++;
                    }else{
                        right--;
                    }
                }
            }
        }
        return list;
    }
}

